use variable names in firebase rules - firebase-realtime-database

I have an existing firebase project. Every user can save data to a 'folder' with the same name as the userid of the user.
I use the rules like this
"$uid":{
".read":"auth.uid == $uid",
".write":"auth.uid == $uid"
}
But now, the need of collaboration between multiple users has risen.
So, i can't use this rule anymore.
I made a new 'table' in firebase, called 'users' where i can save the users id and the according variable workingDir.
Of course, i would like to keep my database secure, but I don't have a clue to setup the firebase rules for that and use this workingDir variable.
Any help is appreciated

Related

Firebase: Maintain a Username Directory

I am creating a Social app and want to track if a username already exists or not. The username list is supposed to grow in future and the way I was doing it now was a key value pair of <string,bolean> like this:
name1: true,
name2: true
all the above data was to be stored in a single document and whenever I want to see if a user exists I would call this document and check accordingly. But here's the problem, firebase max document size is 1MBs and as the users grow this can be problematic, so wanted to know from firebase experts that what's the best way to solve this use case in firestore or realtime database but since I need to query exists maybe realtime db won't suit that well.
Note that I don't want any of firestore querying capabilities but only to check if an entry exists in the record or not and if not just add it.
The Realtime Database doesn't have a 1MB limit (since it has no concept of a document, and everything is just a tree of JSON), so I'd typically use that for the index of user names.
Checking whether a name exists is pretty simple there too, and in JavaScript would look something like:
const usernames = firebase.database().ref('usernames');
usernames.child('name1').once((snapshot) => {
if (snapshot.exists()) {
...
}
});

Swift and Firestore security rules, firebase security

I'm new developer working on my first Firestore app. I've changed the rules on Firestore to make the data more secure for user, but it's not allowing read/write.
This is the key line and I don't know how to configure it specific to my app -
match /some_collection/{userId}/{documents=**} {
I don't know if I change the "some_collection" to my collection name or if some_collection in that sense is an actual wildcard type of parameter itself.
Also, do I need to pass in the userID somehow from my swift application to Firestore? where is userID coming from in this line? I'd prefer to make the rule such that only the user who created the data can read/write. I believe this block is to allow any authenticated user, so I'm just trying to explore each step.
service cloud.firestore {
match /databases/{database}/documents {
// Allow only authenticated content owners access
match /some_collection/{userId}/{documents=**} {
allow read, write: if request.auth != null && request.auth.uid == userId
}
}
}
Addressing your questions:
This is the key line and I don't know how to configure it specific to my app.
match /some_collection/{userId}/{documents=**}
I don't know if I change the "some_collection" to my collection name or if some_collection in that sense is an actual wildcard type of parameter itself.
In the line above "some_collection" is not a firestore wildcard and you need to replace some_collection with the actual value of your collection.
Also, do I need to pass in the userID somehow from my swift application to Firestore?
Yes and it is expected that before reading or writing to/from firestore:
You had already created and configured the firebase object.
firebase.initializeApp({
apiKey: '### FIREBASE API KEY ###',
authDomain: '### FIREBASE AUTH DOMAIN ###',
projectId: '### CLOUD FIRESTORE PROJECT ID ###'
});
You had already authenticated your users with firebase auth.
firebase.auth().signInWithCustomToken(token)
.then((user) => {
// Signed in
// ...
})
.catch((error) => {
var errorCode = error.code;
var errorMessage = error.message;
// ...
});
Passing the userId is done by the firebase object when you call db. collection(“col123”).add or any other method. If you look at how firestore is initialized:
var db = firebase.firestore();
You will see its dependency with the firebase object.
where is userID coming from in this line?
The userID is coming from the firebase object.
I believe this block is to allow any authenticated user, so I'm just trying to explore each step.
Yes, the last rules allow any authenticated user to read and write from/to the subcollections/documents wildcard {userId}.
Lastly it is also expected that there is some naming consistency in the ids of your firestore documents or subcollections.
This means when you create firestore documents, use the firebase.auth.uid as the document id.
Otherwise, the rule from above will fail because the value behind {userId} is not equal to firebase.auth.uid of the logged user.
To achieve the latter, you can refer to this answer.
I highly recommend you have a look at this video(from the firebase channel) since it elaborates more on the core concepts of firestore security rules.
I hope you find this useful.

How to build structured realtime firebase database for iOS, swift?

I am currently setting up my realtime firebase database to my iOS application.
It is my first time trying to structure user data in a firebase database, and I am really, really struggling with understanding a few key things.
A bit of context to my application's database needs:
When a new user is created, the attributes assigned directly to the user are:
Age
Email
Username
Nationality
Later on, the user needs the option of creating personal diaries!
Each of these diaries being arrays/lists of objects... Where each object in a diary furthermore holds a few attributes in a list/array.
After reading everything I could find anywhere, I picture my database something like this:
I am terribly sorry if it becomes too specific - I will try to make the question as open as possible:
My question is:
How to create the different "children" programmatically and how to find the keys leading back to them, so I can refer to them at other times again? (when editing an attribute in a child).
A few methods I have tried:
setValue([ArrayOfObjects]) --> This creates the desired array, but I can't seem to find e.g. index 3 in this array, to allow user to change his/her email later on.
childByAutoID() --> This as well creates my array, but gives several other problems: User can only store one diary, still can't find the paths to specific indexes...
setValue(), andPriority() --> Can't seem to make the priority function. (Is this function also outdated??)
And a few more...
If anyone can tell me how to achieve just the first few steps in setting up my database structure, I will be forever grateful - I have spent literally all day on it and I am not moving forward ...
Or, at least tell me, if I am on the right track regarding my desired setup of the database. Is it flat enough? Is there a smarter way to store all these user created lists?
Thank you so much! :-)
I don't know Swift so my examples are in Dart but the methods are similar I believe.
First off, I would split the Users node into two. One to hold the user data, which is normally pretty static, and the other to hold the diaries. You would use the same uid key as reference to both. This way you have less nesting to worry about and therefore it is much easier to CRUD the data. If you are using Firebase to authenticate your users then I would use the unique key that Firebase creates for each user as the keys for these two nodes.
Then...
To create a user data node record the Dart code would be something like:
referenceUserData.child(<authenticated user id>).set({
"age": <age value>,
"email": <email value>,
"name": <name value>,
});
To create a user diary node object record the Dart code would be something like:
referenceUserData.child(<authenticated user id>).child(<diary key>).child(<diary object key>).set({
"object info value 1": <object value>,
"object info value 2": <object value>,
"object info value 3": <object value>,
});
You could also create all the object records at once by writing them as a List (array) using .set().
You also need to decide what your diary key should be. You could use Firebase to generate a unique key by using .push().set().
To read eg. the user data then your call could be:
referenceUserData
.child(<authenticated user id>)
.once()
.then(
(DataSnapshot snapshot) {
print(snapshot.key);
if (snapshot.value != null) {
print(snapshot.value);
<code to process your snapshot value>
}
};
BTW, 'priority' is legacy from the early days of Firebase RTDB so I wouldn't try to use it.

Only writing data to firebase if information doesn't exist - Swift iOS

I want to only update the values email, firstname and lastname if they are blank.
I need this so that if the user decides to change these in the settings, they are not overwritten every time the user logs in with facebook.
Any solutions to check if the fields are blank without a datasnapshot? Trying to maximise efficency.
Current code when user signs in with facebook?
Database Structure for each user:
One way to do this is using a firebase transaction.
A transaction allows you to check the current value of a DB reference before you set/update it. It's main use case is preventing multiple concurrent updates from multiple sources but it can be used for this case as well - read and then write.
In the transaction block you get the value of the DB ref you're transacting on & can check that the value is null (hence 'create' case) -> then update it as required and return TransactionResult.success(withValue: newData).
If the object is already set you simply abort the transaction with TransactionResult.abort() and no write to the DB is executed.
Another option, that doesn't require a read/write, is to set a Firebase database rule on the relevant ref that will only allow write if the previous value was null:
"refPath": {
".write": "data.val() == null && newDataval() != null"
}
Writing a second time to the DB for an existing ref will fail.
I'd go with the transaction - more expressive of the requirement in the client code.
In firebase the only way you have to check if the current value of your fields in your database are empty is to fetch them before you are setting them.
You can check the field is empty only by fetching them.Then Use this code to update a particular value
ref.child("yourKey").child("yourKey").updateChildValues(["email": yourValue])

Can I create a rule in firebase that will query a value in a push() array?

I only want the user to be able to load the group if they have the group in their list, how would I write a rule for that?
Or is there a way to write a rule to look for a value in a firebase push array?
For example I'd like to write a rule to maybe look like this. This rule isn't valid, but aiming to explain my point with it.
"groups":{
"$group_id":{
".read":"root.child('users').child(auth.uid).child('groups').hasChildValue().val() == $group_id"
}
},
I only want the user to be able to load the group if they have the group in their list, how would I write a rule for that?
Update, how I fixed it.
- Restructuring the data to be flat. Get rid of using push() to add values.
- Flat data made it easy to reference the keys.
"groups":{
// root/users/auth.uid/groups/$group_id
"$group_id":{
// only read if the user has the group_id
".read":"root.child('users').child(auth.uid).child('groups').child($group_id).exists()",
// only write if logged in and it's new || if the user has group id
".write":"(auth != null && !data.exists() && newData.exists()) || root.child('users').child(auth.uid).child('groups').child($group_id).exists()"
}
},
It almost seems like you are trying to 'filter' the group data, which is not what the Firebase rules are for. See link for reference:
https://firebase.google.com/docs/database/security/securing-data#rules_are_not_filters
For what it sounds like you are trying to achieve (restrict read access to groups) you'll need to adjust your data model to the way your app needs to access it. Let me know if this is what you are looking for and I can update my answer.

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